# Patch clamp recordings of action potentials from pyramidal neuron in hippocampus CA1 under focused ultrasound neurostimulation with MEMS self-focusing acoustic transducer

## TL;DR

This study uses focused ultrasound to modulate action potentials in hippocampal neurons, showing both inhibitory and excitatory effects based on stimulation parameters.

## Contribution

A novel neuromodulation platform combining high-frequency focused ultrasound with real-time patch clamp recordings at single-neuron resolution.

## Key findings

- FUS induces both inhibitory and excitatory effects on action potential firing in hippocampal neurons.
- Inhibition was dominant, with optimal results at 60 Vpp, 35 kCycles/pulse, and 100 Hz PRF.
- Excitation was mainly due to thermal effects, observed at 120 Vpp, 50 kCycles/pulse, and 20 Hz PRF.

## Abstract

Objective. This study aims to investigate the modulatory effects of focused ultrasound (FUS) on neuronal activity at the single-cell level, using whole-cell patch clamp recordings in hippocampal slices. Approach. A self-focused acoustic transducer (SFAT) was designed and fabricated on a 127 µm-thick translucent lead zirconate titanate substrate to allow infrared light transmission for visualizing neurons during patch clamp experiments. The SFAT operates at 18.4 MHz, producing low-intensity FUS with a 46 µm focal diameter at a depth of 400 µm. Three types of SFAT—active, FUS-blocking control, and low-electromagnetic interference (EMI) versions—were developed to assess the effects of acoustic stimulation, thermal heating, and EMI. Neuronal responses were recorded across 78 tissue samples from 29 animals using 48 combinations of acoustic parameters, including peak-to-peak voltage, pulse repetition frequency (PRF), and pulse duration. Main results. Whole-cell patch clamp recordings from CA1 pyramidal neurons in rat hippocampal slices revealed that FUS induces both inhibitory and excitatory effects on action potential firing, depending on the stimulation parameters. Inhibition was found to be the dominant response, while excitation was mainly attributable to thermal effects. Optimal inhibition was achieved with 60 Vpp (ISAPA = 2.11 W cm−2), 35 kCycles/pulse (1.90 ms), and 100 Hz PRF, yielding a 60% success rate. Conversely, excitation was observed in 60% of trials using 120 Vpp (ISAPA = 8.44 W cm−2), 50 kCycles/pulse (2.72 ms), and 20 Hz PRF. Significance. This work presents a novel neuromodulation platform that combines high-frequency focused ultrasound with real-time whole-cell patch clamp recording at single-neuron resolution. The results provide direct electrophysiological evidence of parameter-dependent, bidirectional modulation of neuronal activity by FUS, offering new insights into its underlying mechanisms and helping define stimulation protocols for future neurotherapeutic applications.